In general, a power distribution system includes a high-voltage system (e.g., 3300 volts to 6600 volts) and a low-voltage system (e.g., 100 volts to 200 volts). Receiving terminals of general consumers are connected to the low-voltage system. A power company is obliged to maintain the voltage at the receiving terminals of the general consumers within a proper range (e.g., in the case of power reception of 100 volts, the voltage is maintained between 95 volts and 107 volts). Therefore, the power company maintains the voltage at the receiving terminals of the general consumers by adjusting a control amount (e.g., operating a tap) of a voltage control device (e.g. an LRT (Load Ratio Control Transformer) or an SVR (Step Voltage Regulator)) connected to the high-voltage system. Note that, in the following explanation, a power distribution system indicates the high-voltage system.
Conventionally, concerning voltage control of the power distribution system, a local voltage control apparatus is generally spread that is integrated with a voltage control device of a transformer type, such as an LRT or an SVR, or provided side by side with the voltage control device and performs voltage control on the voltage control device in an autonomous distributed type based on measurement information (a voltage and a power flow) near a setting point of the voltage control device. Note that, as the voltage control device, besides the voltage control device of the transformer type, there is known voltage control devices of a reactive power control type, such as automatic ON/OFF phase modifying equipment (a static capacitor, a shunt reactor, etc.), an SVC (Static Var Compressor), and a PCS (Power Conditioning System) with a reactive power adjusting function. Local voltage control apparatuses respectively corresponding to these voltage control devices are also put to practical use. The PCS is, for example, a power conditioner for solar power generation. The PCS connects solar power generation equipment or a storage battery and a power distribution system.
These local voltage control apparatuses are configured on the premise that a load distribution of a power distribution system is uniform, that is, voltages at respective points of the power distribution system change in the same direction according to the elapse of time. However, in recent years, because of the diversification of a way of using electricity, the spread of a distributed power supply due to solar power generation, and the like, the load distribution of the power distribution system tends to fluctuate greatly in a non-uniform manner according to the elapse of time. Therefore, it is difficult to maintain a proper voltage with the conventional voltage control of the power distribution system.
Therefore, instead of the voltage control system of the autonomous distributed type, it is proposed to centrally control a voltage of a power distribution system in a consistent form in the entire system (a centralized control system). Specifically, a scheme is proposed in which measurement information (voltages and power flows) at a plurality of points in the power distribution system is collected in a centralized voltage control apparatus using a dedicated network, the centralized voltage control apparatus determines control amounts (tap positions, etc.) of respective voltage control devices based on these measurement information, and the control amounts for the voltage control devices are automatically remotely commanded from the centralized voltage control apparatus (see, for example, Patent Literatures 1 to 3).
Note that, a plurality of schemes are studied and disclosed concerning a technology for predicting and correcting a solar power generation amount according to an increase of solver power generation, a technology for separating a power flow value of a distribution line into a solar power generation amount and an actual load, a technology for estimating load distributions at respective system points from a power flow value of a distribution line, and the like (see, for example, Patent Literatures 1 to 3).